The present invention relates to a striking mechanism of a clock.
Striking mechanisms with hammers have long been known in clock movements for generating sounds in the audible range, in that they are mounted to be rotatable around an axis and on their edge have a striking edge, which strikes against a circular gong, for example, when the hammer is rotated by a pre-tensioned drive spring. The oscillation of this gong then generates a desired noise and timbre.
In order to tension the drive spring and accordingly move the striking edges of the hammers away from the gongs prior to the strike, so-called leverages are provided, which cooperate with pins arranged on the hammers, and are controlled by a striking mechanism provided, inter alia, with racks. The majority of hammers can be utilised, for example, in minute repeater striking mechanisms in order to generate different sounds.
However, to prevent the hammers from touching the gongs when in their respective rest positions and to thus allow the gongs to oscillate freely after the strike, so-called countersprings are provided, which are generally made from a harder material than the drive springs and press against the same pin in the opposite direction to the drive spring. The distance between the gong and the striking edge is then arranged by adjusting the positioning of the counterspring in such a manner that there is always a space between these two parts after the strike, and therefore any unwanted additional strikes are prevented.
A minute repeater striking mechanism that uses such an arrangement of hammers is illustrated, for example, in page 219 of the book Théorie d'horlogerie by Reymondin, Monnier, Jeanneret, Pelaratti. In conventional clocks comprising such a repeater striking mechanism, the stop of the hammer is released as follows: the pin fastened in the rotatably mounted hammer reaches an end stop at a counterspring screwed onto the plate. This counterspring at the same time has an arm provided with elastic properties and a stable non-elastic arm on the opposite side. An adjusting screw provided with a point presses against this arm. If this adjusting screw is now turned to the right, the point presses against the non-elastic arm of the counterspring and at the same time the elastic arm moves the hammer via the pin in a corresponding direction. If the adjusting screw is turned in the other direction, i.e. the point of the screw moves away from the non-elastic arm, then the counterspring stays in its position. However, to change the position of the counterspring, the fastening screw must be released, and this is only possible if the hands and dial are disassembled.
A similar structure of hammers and countersprings for a striking mechanism is described in the patent document CH 706190, according to which the counterspring is screwed from the dial side and where the adjustment of the position of the counterspring is achieved by means of an eccentric provided with a pin, which is accessible from the dial. The eccentric presses against a hard rear flank of the counterspring in order to move it around its swivel axis.
A disadvantage of these known mechanisms is that the number of parts of the striking mechanism is very high and therefore the entire assembly is particularly long. A further disadvantage is that the adjustment of the rest position of the hammers is delicate, because the fastening screw of the counterspring must be released beforehand and, on the other hand, the adjusting screw adjusting screw is only accessible from the dial side, which renders subsequent correction particularly difficult.